In rotating dobbies, the reciprocating vertical movement of the heddle frames is ensured by connecting rod/oscillating lever assemblies, such oscillating assemblies being controlled by actuation elements in the form of eccentrics. Such actuation elements are mounted on a principal shaft of the dobby which is animated by an intermittent movement of rotation and, whenever this shaft stops, a reading device controls the connection of the actuation element with the shaft in order to control an oscillating piece as a function of the design or weave to be obtained on the fabric being woven.
FR-A-2 540 524 discloses a rotating dobby in which such selective connection is obtained thanks to a plate fast with an eccentric forming actuation element and comprising two diametrally opposite notches adapted to cooperate with the catch of two pivoting levers controlled by a reading device. Furthermore, FR-A-2 757 884 discloses using a pivoting selector intended to selectively actuate one or the other of two pivoting levers of the type mentioned above. This selector is controlled thanks to an electromagnet and subjected to the action of return means. As for FR-A-2 757 882, it teaches providing that, when the pivoting levers are in mesh with certain jamming surfaces provided on a plate, they are out of range of a selector.
In the known devices, particularly those known from FR-A-2 757 882 and FR-A-2 757 884, the mobile assembly forming selector or actuator comprises a pusher which is used for displacing one or the other of the pivoting levers against return efforts to which they are subjected. This pusher must therefore be sufficiently robust to perform this function and the electromagnet which controls it must be powerful, which in practice amounts to increasing its size to such a point that it is not necessarily compatible with the division corresponding to the thickness of the heddle frames of the loom. In addition, the energy necessary for controlling the pusher considerably increases at high speed, which imposes dimensioning this pusher and the electromagnet accordingly. Finally, the electromagnet associated with the pusher is subjected to accelerations and to intense vibrations, which reduces its life duration.
It is a more particular object of the present invention to overcome these drawbacks by proposing a novel arrangement which makes it possible to mechanically stress the pusher of the reading device and the electromagnet associated therewith to a lesser degree, while ensuring a secured functioning of the dobby.